Lesion development in stems of rough‐ and smooth‐barked Eucalyptus nitens following artificial inoculations with canker fungi

Abstract

A study of lesion development in stems of Eucalyptus nitens following artificial inoculations with canker fungi was carried out on 16‐year‐old plantation trees. In a first trial cambium bark wounds on smooth‐ and rough‐barked trees were inoculated with the mycelium of nine species of canker fungi, including Endothia gyrosa. In a second trial spores or mycelium of E. gyrosa were applied directly onto undamaged or superficially wounded bark surfaces. Infection subsequent to artificial inoculation via wounding (whatever the wounding technique or type of inoculum) resulted in significantly larger external lesions (mean lesion area up to 35.6 cm2 20 months after inoculation) on smooth bark compared with those on rough bark (up to 19.0 cm2). Microscopic studies of infected rough and smooth bark suggest that, once smooth bark is compromised by wounding and artificial inoculation, the particular anatomical structure of smooth bark may offer less mechanical resistance to post‐penetration hyphal spread in comparison with rough bark. It is suggested that at a pre‐penetration stage under natural conditions spores of E. gyrosa more easily infect rough bark via cracks associated with this type of bark but not present in smooth bark.

Seiridium (Sporocadaceae): an important genus of plant pathogenic fungi

“…Seiridium eucalypti is known to inflict lesions on a wide range of Eucalyptus spp. Its pathogenicity to members of Eucalyptus was studied in detail by Yuan & Old (1995) and Yuan & Mohammed (1997 , 1999 , 2001) . The strain examined in this work (CBS 343.97) matches the protologue of S. eucalypti ( Nag Raj 1993 ), and is therefore designated as epitype.…”

“…have been observed in Eucalyptus spp. ( Myrtaceae ) ( Yuan & Old 1995 , Yuan & Mohammed 1997 , 1999 , 2001 ), and recently, S. phylicae was described ( Crous et al 2012 ), which is an aggressive pathogen of Phylica arborea ( Rhamnaceae ), endemic to the archipelago Tristan da Cunha ( Ryan et al 2014 ). Furthermore, less destructive and perhaps more opportunistic pathogens are common to the genus, such as the generic type S. marginatum , for example.…”

TheEucalyptuscanker pathogenChrysoporthe cubensisdiscovered in eastern Australia

“…Wardlaw (1999) also identified H. eucalypti in fine cracks in the new bark of rough-barked trees and suggested the presence of this suitable infection court differentiated rough bark from smooth bark in terms of infection. Yuan and Mohammed (2001) also found (using artificial inoculation studies) that cankers formed on smooth-barked trees and surmised that the absence of cracks in smooth-barked trees was significant at the pre-penetration stage under conditions of natural infection. Chr.…”

Host responses to natural infection by Cytonaema sp. in the aerial bark of Eucalyptus globulus

“…This process involves the formation of a ligno-suberized boundary zone in cells present at the time of wounding while underlying healthy bark tissue near the lesion margins de-differentiates to form a wound periderm (WP) (Mullick 1977;Woodward and Pearce 1988a;Biggs 1992;Solla et al 2002). This has also been true for the few studies that have investigated the host responses of bark to fungal infections in Eucalyptus (Tippett et al 1983;Tippett and Hill 1984;Wardlaw 1999;Yuan and Mohammed 2001). phenolic and terpenoids compounds have been reported to accumulate in the lesion margin (LM), particularly in gymnosperms (Woodward and Pearce 1988b;Klepzig et al 1995;Virri et al 2001).…”

“…For the broadleaved angiosperms however, studies of the host responses to canker infection have predominantly focused on the histological aspects of bark resistance while the chemistry of wound responses in bark has received little consideration. This has also been true for the few studies that have investigated the host responses of bark to fungal infections in Eucalyptus (Tippett et al 1983;Tippett and Hill 1984;Wardlaw 1999;Yuan and Mohammed 2001). Until recently, chemical analyses of this relatively large genus have generally focused on determining the chemistry of healthy bark (Cadahia et al 1997a;Lee et al 1998;Kim et al 2000), leaves (Boland et al 1991;Close et al 2001), healthy wood (Cadahia et al 1997b) and kino, a polyphenolic exudate (Hillis and Carle 1962;Hillis and Yazaki 1975).…”